1. Field of the Invention
The present invention relates to a machine tool and, in particular, to a machine tool that controls a working path for removing a burr from workpiece.
2. Description of the Related Art
In individual pieces of workpiece, burrs which are different from one another in units of millimeters often appear. For this reason, when burring is performed on workpiece by using a machine tool, a program is created with reference to a piece of workpiece in which the largest number of burrs have appeared. In this case, in working which is performed on a piece of workpiece in which less burrs have appeared than the piece of workpiece used as reference workpiece, air cut (idle operation) is frequently performed, resulting in wasted time in which working is not performed.
Furthermore, depending on the location or direction in which a burr has appeared, it is difficult to perform burring from the main axis direction of the machine tool. In such a case, it is necessary to perform burring by tilting the workpiece by using an additional axis table, perform burring in another process by executing a tooling change, or perform burring manually.
On the other hand, as a prior art technique of performing burring, in Japanese Patent Application Laid-Open No. 2007-021634, Japanese Patent Application Laid-Open No. 07-104829, and Japanese Patent Application Laid-Open No. 07-121222, for example, techniques of automating burring by using a robot by generating a working path from the information obtained by a visual sensor are disclosed. In general, since a robot has a higher degree of flexibility in operation than a machine tool, the robot relatively easily performs working on burrs that have appeared in various locations and directions.
However, in the techniques disclosed in Japanese Patent Application Laid-Open No. 2007-021634 and Japanese Patent Application Laid-Open No. 07-121222, a robot can hold only a small tool and the torque of the robot that can withstand working is low. As a result, it is necessary to ease working conditions in an area in which a large burr has appeared, which undesirably lengthens the working time. Moreover, working becomes impossible depending on the dimensions of a burr.
In addition, in the technique disclosed in Japanese Patent Application Laid-Open No. 07-104829, a robot can select a tool and working conditions in accordance with the dimensions of a burr. Here, the robot has to use a tool whose diameter is larger than the dimensions of a burr. However, the larger the tool becomes, the worse the working conditions become, which undesirably lengthens the working time. Moreover, working becomes impossible depending on the dimensions of a burr.